Could someone explain to me in terms of bonding and at an atomic level why sulphuric acid is strong?

Question

thanks

Answer 1

In a molecule of H2SO4, or in any oxoacid, the H-O bonds are polar because the oxygen is more electronegative than hydrogen. This means the hydrogen carries a partial positive charge. Anything that can affect how polar this bond is will also affect the acidity. Making the H-O bond more polar gives the hydrogen a greater partial positive charge and makes it easier for it to come off as H^+1.

The number of lone oxygen atoms bonded to the central sulfur atom will increase the acidity. Oxygen is a very electronegative element and the S=O bonds are polar with the negative charge concentrated about the oxygen. In other words the lone oxygen atoms draw electrons away from the sulfur making the sulfur more positive. Thus, in H-O-S the positive sulfur wants to draw electrons from the H-O. The oxygen is electronegative and doesn't want to give up its electrons, so the electrons come from the H-O bond, making the H even more positive and more likely to come off as H^+1.

Answer 2

I think it's too do with dissociation. All acids have a H atom, and when added to water, sulphuric acid's H atom dissociates from the SO4 molecule, forming H+ and SO4-. The fact that all molecules release a H+ ion means the acid is strong, whereas a weak acid, such as CH3COOH, does not totally dissociate, only releasing a few H+ ions.

Answer 3

Technically when one speaks of 'strong' or 'weak' acids, they are refering to the acid's ability to dissociate in water....thus giving ions, two of which eventually exist as H+ or protons, increasing acidity within the solution. The water assists acids due to its polar nature, ionizing an acid. H2SO4 is an acid which technically donates its protons in water, however is a diprotic acid which undergoes two separate reactions of doing so:

H2SO4 ------> HSO4^- + H+

HSO4^- --------> SO4 ^-2 + H+